Biomedical subjects

A Lagi

Publications and source records attributed to A Lagi.

At least 19 recordsLinked to original sources

PubMed2001

Cerebral vasoconstriction in vasovagal syncope: any link with symptoms? A transcranial Doppler study.

BACKGROUND: Cerebral vasoconstriction has been described previously in vasovagal syncope (VVS). This phenomenon appears paradoxical in view of the well-known decrease of systemic vascular resistances taking places during VVS. We aimed to assess (1) whether cerebral vasoconstriction in VVS is an independent paradoxical phenomenon and (2) whether cerebral vasoconstriction has any link with symptoms and/or VVS onsets. METHODS AND RESULTS: Seven young patients with recurrent VVS participated in the study. Each patient underwent monitoring of heart rate, blood pressure, cerebral blood flow velocity (by means of transcranial Doppler), end-tidal PCO(2), peripheral oximetry, respiratory rate, and tidal volumes both at rest and during head-up tilt. All the subjects experienced tilt-induced VVS. A significant increase of respiratory tidal volumes was observed in each subject >/=160 seconds before VVS. This deep breathing induced a PCO(2) decrease and, consequently, also a decrease in cerebral blood flow velocity and increase in cerebrovascular resistance (expressed by the increase of the pulsatility index). Within 40 seconds, 5 subjects started complaining of discomfort, in the absence of any significant blood pressure drop. CONCLUSIONS: Cerebral vasoconstriction is not a paradoxical phenomenon when it occurs before tilt-induced VVS but rather is only the physiological consequence of the hyperventilation-induced hypocapnia that occurs in habitual fainters. The large lag between the onset of syncope and cerebral vasoconstriction excludes the hypothesis that VVS is dependent on abnormal behavior of cerebral hemodynamics.

Adolescent↗

PubMed2000

Disease-related syncope. Analysis of a community-based hospital registry.

Syncope is characterized by sudden and transient loss of consciousness that follows a reduction or interruption of cerebral blood flow. The present study was designed to assess the prevalence of disease-related syncope in a wide sample of in-patients admitted for different diseases. A total of 16 809 patients (age range 18-99 years) were recruited from three hospitals in Florence in 1998. The community-based registry was reviewed to identify all patients suffering from complaints associated with syncope. Each disease-related syncope was matched with the number of patients suffering from that disease. Furthermore, each disease was expressed as a percentage of total cases included in the study. The odds ratio was calculated to determine the index of significant correlation between syncope and occasional diseases. Total syncopes were 775 (prevalence 4.46%), vasovagal syncopes were 336 (1.9% of total sample and 44% of total syncopes), and the disease-related syncopes were 439 (56% of total syncopes). We found a significant association between syncope and orthostatic hypotension, complete heart block, chronic cerebral disease, migraine, acute gastrointestinal haemorrhages and aortic stenosis. Furthermore, we found a significant association with acute gastrointestinal haemorrhage, which has not been described previously. Significant relationships emerged from our data which yield a new insight into the association between syncope and a wide range of systemic diseases.

Adolescent↗

PubMed1999

Age-related changes of cardiac parasympathetic modulation after vasovagal syncope.

The time-domain analysis of 24-hour electrocardiographic recordings showed that vagal modulation of heart rate is reduced within 48 hours from vasovagal syncope. However, patients with recent vasovagal syncope can be differentiated from healthy subjects only up to the age of 40 years with this analysis, because this parasympathetic modulation physiologically decreases with increasing age.

Adolescent↗

PubMed1999

Autonomic control of heart rate variability in vasovagal syncope: a study of the nighttime period in 24-hour recordings.

Patients experiencing vasovagal syncope have been claimed to show reduced vagal tone over 24-hour electrocardiography recordings. Assessment of sympathovagal balance in the absence of external stimuli, i.e., nighttime electrocardiography monitoring, might help to clarify if increased sympathetic activity is present in these patients. Heart rate variability was examined at nighttime in 40 patients with recurrent episodes of vasovagal syncope within the last 2 years (22 men; mean age, 37 years) and 20 comparable healthy volunteers. Time domain parameters (pNN50 [proportion of successive RR intervals difference >50 ms in %] and rMSSD [root-mean-square successive difference of RR intervals in ms]), indexes of vagal tone, and frequency domain parameters, expressing the overall heart rate variability, vagal (high frequency [HF]) and sympathetic (low frequency [LF]) activity, and autonomic balance (LF/HF ratio) were compared between groups by Mann-Whitney test. Significant (p<0.05) reduction of heart rate variability and vagal tone (pNN50 and rMSSD) were found for patients with vasovagal syncope, together with increased sympathetic activity (increased LF/HF ratio). These findings could open new insights in the pathogenesis of vasovagal syncope because of the shift of the autonomic balance toward sympathetic activation near the syncopal episode.

Adult↗

PubMed1999

Autonomic control of the cerebral circulation during normal and impaired peripheral circulatory control.

OBJECTIVE: To determine whether oscillations in the cerebrovascular circulation undergo autonomic modulation in the same way as cardiovascular oscillations. DESIGN: Cardiovascular and cerebrovascular oscillations were monitored at rest and during sympathetic stimulation (head up tilt). The association with and transmission of the oscillations in the sympathetic (low frequency, LF) and respiratory (high frequency, HF) bands was assessed. SUBJECTS: 13 healthy volunteers, 10 subjects with vasovagal syncope, and 12 patients with complicated non-insulin dependent diabetes mellitus. MAIN OUTCOME MEASURES: Power spectrum analysis of cerebral blood flow velocity, arterial blood pressure, and heart rate. Coherence analysis was used to study the association between each pair of oscillations. Phase analysis showed the delay of the oscillations in the cardiovascular signals with respect to the cerebrovascular signals. RESULTS: The power in the sympathetic (LF) components in all the oscillations increased during head up tilt (p < 0.01) in the controls and in the subjects with vasovagal syncope, but not in patients with diabetes. Significant coherence (> 0.5) in the LF band was present between cerebrovascular and cardiovascular oscillations in most of the controls and in subjects with vasovagal syncope, but not in the diabetic patients (< 50% of the patients). In the LF band, cerebrovascular oscillations preceded the cardiovascular oscillations (p < 0.05) at rest in all groups: the phase shifts were reduced (p < 0.05) during head up tilt for all cardiovascular signals in healthy and syncopal subjects, but only for heart rate in diabetic patients. CONCLUSIONS: The cerebrovascular resistance vessels are subject to autonomic modulation; low frequency oscillations in cerebral blood flow velocity precede the resulting fluctuations in other cardiovascular signals. Autonomic neuropathy and microvascular stiffness in diabetic patients reduces this modulation.

Adult↗

PubMed1997

Vagal control of heart rate variability in vasovagal syncope: studies based on 24-h electrocardiogram recordings.

The autonomic nervous system has an important role in the pathophysiology of vasovagal syncope. The purpose of this investigation was to evaluate to what extent the autonomic system is involved in the mechanism of fainting and to characterize the profile of heart rate variability of individuals who are prone to undergo a critical event. Thirty patients (mean age 41 years) with vasovagal syncope and 15 comparable controls were monitored by 24-h electrocardiography. Heart rate variability was analysed over the whole 24 h and during the daytime and night-time using time domain parameters (average of heart periods, RR; standard deviation of heart periods, SDNN; standard deviation of the average of RR intervals over all the 5-min segments of the entire recording, SDANN; percentage of the total number of all RR intervals of pairs of adjacent RR intervals differing more than 50 ms over the entire recording, pNN50; the square root of the sum of the square of differences between adjacent RR intervals, rMSSD), as indicated by the Task Force for Clinical Use of Standard Measurements of Heart Rate Variability. These parameters explore the influence of the autonomic nervous system on sinus node function and provide information about the vagal control to the heart. Among these parameters, pNN50 and rMSSD were significantly reduced in individuals with vasovagal syncope when compared with controls, over each time period considered. The two parameters are related to high-frequency oscillations in the frequency domain and to the vagal influence of the heart. These results indicate that the vagal tone to the heart is altered in subjects who suffer from vasovagal syncope. The results of this study provide an insight into the pathophysiological mechanism of fainting and may offer another means of evaluating patients with syncope.

Adolescent↗

PubMed1997

Cerebral autoregulation in patients with cirrhosis and ascites. A transcranial Doppler study.

BACKGROUND/AIMS: Patients with cirrhosis and ascites usually show alterations of systemic hemodynamics and are thus prone to develop arterial hypotension, which might result in cerebral hypoperfusion if cerebral autoregulation is impaired. METHODS: We evaluated cerebral autoregulation in 15 patients with cirrhosis and ascites and 15 healthy subjects by monitoring mean blood flow velocity in the middle cerebral artery and arterial pressure during supine rest and passive tilting. RESULTS: Tilt provoked a drop of arterial pressure in both groups. Control subjects had a prompt recovery of mean flow velocity and a progressive recovery of arterial pressure, so that, after 120 s, both parameters had returned to baseline: at 20 s the recovery of flow velocity was faster (p<0.01) than that of blood pressure. By contrast, patients with cirrhosis had a delayed and incomplete recovery of both parameters (p<0.01 vs healthy subjects). In eight patients, the recovery of mean flow velocity paralleled that of arterial pressure, indicating an impaired cerebral autoregulation. These patients had a worse liver function, a higher cardiac index and lower peripheral resistance. CONCLUSIONS: Cerebral autoregulation is often impaired in patients with cirrhosis and ascites. These patients can develop cerebral hypoperfusion if arterial pressure falls abruptly.

Aged↗

PubMed1997

Effect of PCO2 changes induced by head-upright tilt on transcranial Doppler recordings.

BACKGROUND AND PURPOSE: Transcranial Doppler (TCD) monitoring of mean blood flow velocity (mV) during head-upright tilt can allow testing of cerebral autoregulation. Nonetheless, head-upright tilt can induce changes in the ventilation-perfusion relationship and/or respiratory activity that might influence TCD data. METHODS: Forty-eight healthy volunteers underwent monitoring of mV and end-tidal CO2 in the horizontal position and during head-upright tilt. RESULTS: Both mV and end-tidal CO2 significantly decreased in orthostasis (P < .01). Linear regression analysis showed a significant linkage between end-tidal CO2 and mV changes (r = .83, P < .01). CONCLUSIONS: Changes in ventilation-perfusion ratio and in the respiratory pattern induced by head-upright tilt can significantly influence TCD data by determining a PCO2 decrease.

Adult↗

PubMed1996

Heart rate and blood pressure variability in orthostatic syncope.

The pathogenetic role of autonomic nervous system in the neurally mediated orthostatic vasodepressive syncope is unclear. upright tilt was used to assess the characteristics of autonomic tone during orthostatic stress. We studied 18 patients (mean age 26 +/- 5 years) suffering from vasodepressive orthostatic syncope and with positive response to a 30-minute 60 degrees upright tilt and a comparable control group with a negative response to the upright tilt test. Blood pressure and heart rate (RR Interval) were measured beat-by-beat; ECG, systolic (SAP) and diastolic arterial pressure (DAP) and respiration trace were recorded for spectral analysis. The most important result of the work is a different pattern of the parameters evaluated, between fainters and controls, in the last period of tilt test, just before the syncope, and in the fainters group between the first (at the beginning) and the last period (just before syncope) of tilting. Baseline heart rate, arterial pressure and spectral indices were similar and increased with tilting in both groups (Low Frequency: LF; High Frequency: HF; LF/HF ratio). Just before the syncope, we observed in fainters group a decrease of heart rate, blood pressure, LF-RR, LF-DAP, LF-SAP, LF/HF -RR, and an increase of HF-RR and of total power where compared to in the same subjects in the first period of tilt and in front of controls in the same period of tilt. The novel aspect of the work, regarding the autonomic control of heart rate and arterial pressure, expressed by spectral fluctuations and by haemodinamic parameters, is consistent with a reduced sympathetic reserve in the immediate pre-syncopal period.

Adult↗

PubMed1996

Impaired cardiovascular autonomic response to passive tilting in cirrhosis with ascites.

The autonomic regulation of cardiovascular function was evaluated in 15 cirrhotic patients with ascites and in 13 healthy subjects by the autoregressive power spectral analysis (PSA) of the intervals between adjacent R waves of the electrocardiogram (RR) interval and arterial pressure variability. Total power, low frequency (LF; index of the sympathetic activity of the heart and circulation), and high frequency (HF; index of vagal tone to the heart) components of the RR interval, systolic, and diastolic arterial pressure were evaluated in the supine position and during passive tilting, together with plasma norepinephrine levels. In the supine position, no significant differences in the PSA data were observed between the control subjects and cirrhotic patients, who had higher plasma norepinephrine levels. In healthy subjects, tilting was associated with an increase in the LF of the RR interval and arterial pressure and a decrease in the HF of the RR interval. In contrast, patients with cirrhosis showed a decrease of both LF and HF. Consequently, the LF/HF ratio significantly increased in healthy subjects, whereas it was unchanged in cirrhotic patients. The LF component of the diastolic pressure also decreased during tilting in cirrhotic patients. Plasma norepinephrine increased after tilting in both groups. These results indicate that the autonomic response to passive tilting is impaired in cirrhotic patients with ascites at both the cardiac and vascular levels, as a result of an altered sympatho-vagal balance, with reduced sympathetic predominance. These alterations occurred despite an appropriate response to the tilting of plasma norepinephrine, pointing to a receptorial or postreceptorial site of the autonomic impairment.

Adult↗

PubMed1994

Observations on the arterial baroreflex in neurally mediated vasodepressor syncope.

The arterial baroreflex was studied in subjects who had recently had an episode of vasodepressor syncope. This was determined using 2-3 mcg/kg intravenous boluses of phenylephrine and assessing the bradycardic response. The values were measured in ms/mmHg and expressed as the angular coefficient of the regression line between the increase in R-R interval on the electrocardiograph and the systolic arterial pressure. In subjects examined immediately after the vasodepressor syncope episode the bradycardic response was much more marked than in controls (p < 0.01) and in the subjects themselves 6 months after the episode, provided that they were symptom-free (p < 0.01). It is concluded that in vasodepressor syncope there is a phase in which the baroreflex is highly sensitive and that this is due not to a lowering of the stimulation threshold but to a gain in the efferent arc, which explains a 'vagotonic' response.

Adolescent↗

PubMed1994

Power spectrum analysis of heart rate variations in the early detection of diabetic autonomic neuropathy.

Power spectrum analysis of the R-R interval was used in 20 controls and in two groups of type I (insulin dependent) diabetics (27 patients) to detect changes in total power or in its components (low frequency and high frequency) that might be considered an early evidence of impairment of cardiac autonomic nervous system control. A significant difference between controls and severe diabetics (with autonomic involvement) was found in all components. In the early stage of diabetes without evidence of autonomic involvement, an absolute reduction of the low frequency component in the standing position and a significant reduction of the percentage increase compared with the lying position, was found to discriminate diabetics from controls. The occurrence of somatic neuropathy was unrelated to changes in autonomic function. These data indicate that: (1) power spectrum analysis is sensitive enough to detect cardiac autonomic neuropathy in diabetics, where standard methods fail; (2) power spectrum analysis is the method of choice in the early stages; (3) in severe type I dependent diabetes there is a reduction of power spectrum analysis total power and a defective response to standing up; (4) cardiac autonomic neuropathy develops independently from somatic neuropathy.

Adult↗

PubMed1994

Cerebral autoregulation in orthostatic hypotension. A transcranial Doppler study.

BACKGROUND AND PURPOSE: Transcranial Doppler measurements of blood flow velocity permit an assessment of variations in intracranial hemodynamics in response to acute arterial pressure variations. The purpose of this study was to scan healthy volunteers and patients with autonomic failure for differences in cerebral hemodynamic patterns under an acute hypotensive stimulus. METHODS: We used transcranial Doppler monitoring of blood flow velocity in the middle cerebral artery and noninvasive monitoring of arterial blood pressure and heart rate before, during, and after acute arterial hypotension induced by reactive hyperemia of the lower limbs. RESULTS: After maximum hypotension, the mean blood flow velocity was higher in the healthy volunteers than in the patients. In the healthy subjects mean velocity rose significantly (P < .01) higher than arterial blood pressure after 30 seconds and 60 seconds; in the patients mean velocity and arterial pressure moved in parallel fashion. The diastolic blood flow velocity increased more in the control group than in the patients during the early stages of the test; furthermore, only in the healthy volunteers did it increase significantly more than arterial pressure after 30 seconds and 60 seconds. Regarding the pulsatility index, the differences between the two groups were similar to the diastolic velocity results. CONCLUSIONS: (1) Monitoring of mean blood flow velocity showed the ability to maintain an adequate cerebral blood flow in healthy subjects; this mechanism was not efficient in the patients with autonomic failure. (2) Diastolic velocity and pulsatility index values clearly showed that only in healthy subjects were cerebral hemodynamics relatively independent of pressure values.

Blood Flow Velocity↗

PubMed1993

Mitotic activity in colorectal mucosa of healthy subjects in two Italian areas with different dietary habits.

The proliferative activity was evaluated in colorectal biopsies of 39 healthy subjects living in two distinct geographical areas, Trieste in northern and Florence in central Italy. Subjects living in Trieste had a significantly higher mitotic activity compared with subjects living in Florence (mitoses/cells counted x 100 were 0.17 +/- 0.04 in Trieste and 0.089 +/- 0.02 in Florence). The results of a dietary questionnaire also showed that subjects in Trieste consumed significantly fewer starches, fibers, nitrites, and proteins. However, no correlation was evident between the consumption of these nutrients and intestinal proliferation.

Adult↗

PubMed1993

Blood pressure and heart rate relationship in normotensive and hypertensive subjects.

A twenty-four-hour blood pressure (BP) monitoring was performed in 20 normotensive and 20 hypertensive subjects, matched by sex and age. Blood pressure and heart rate (HR) variability were evaluated both as absolute and percent standard deviation. In agreement with the literature no significant difference in HR and BP variability was observed between the two groups. The linear regression between HR and BP values was evaluated in both groups. The authors observed a significant difference in the relationship between these two cardiovascular variables between the two groups. In the hypertensive group the cardiovascular control of HR and BP showed a different relationship than in normotensive subjects, suggesting a different neurovegetative modulation.

Adult↗

PubMed1992

The tilting cardiovascular response in orthostatic syncope.

159 patients with a previous discharge diagnosis of recurrent vasodepressor syncope associated with prolonged standing or other circumstance known to trigger the condition were examined in order to isolate the orthostatic form. 72 patients with a history of at least two episodes of loss of consciousness after standing still for at least 10' were selected for testing by head-up tilt. Those who showed signs or symptoms during the test were tested a further twice, the third time after atropine administration. This process resulted in the diagnosis of orthostatic vasodepressor syncope in 28 patients who presented both 1) a positive test associated with hypotension and bradycardia and 2) bradycardia-free hypotention on repetition of the test with atropine.

Adolescent↗

PubMed1992

[Diagnosis of cardiocirculatory autonomic failure by the tilting method].

The variation of SBP, DBP and HR is evaluated on tilting in a group of 34 patients affected by orthostatic hypotension versus a group of 54 healthy subjects, age and sex cross-matched. The patients affected by cardiovascular autonomic failure showed: 1) a fall of SBP greater than -19 mmHg in the 1st min; 2) a fall of the SBP average value (for 10 minutes) greater than -22 mmHg. Contrarily, the healthy subjects showed: 1) no variations of SBP values during the 1st minute and 2) a growing of SBP between the 2nd and the 10th minute; 3) a SBP average value (for 10 minutes) with a positive trend. The DBP and HR showed not differences between the groups. We suggest that the measure of SBP on standing may be considered an easy and fast method to perform a diagnosis of autonomic cardiovascular failure.

Adult↗

PubMed1992

[Pulmonary embolism. A case report of right atrial thromboembolism treated by thrombolysis].

This case report describes a 40-years-old man affected by fracture of leg and pulmonary embolism. Two-dimensional echocardiography showed a large right atrial migrant thromboembolus prolapsing into tricuspid valve during diastole. The patient was treated with rt-PA through right atrial venous catheter and underwent to serial echocardiographic examinations. The rt-PA determined the dissolution of the thrombo-embolus at the 2nd hour of infusion. It is concluded that early two-dimensional echocardiography might be a very helpful technique to diagnose and follow-up therapy of pulmonary embolism.

Adult↗